Not for the first time, the House GOP has an idea that has no chance of passing the Senate or President Obama's desk. It wants to avoid a government shutdown on Oct. 1 by passing a temporary government funding bill – called a continuing resolution – that has one humongous asterisk: It would not include any money for Mr. Obama's health-care reform law. In essence, the House GOP is saying: Defund Obamacare or we shut down government.

The fight has exposed deep fault lines within the GOP and resulted in a virtual revolt against House Speaker John Boehner. Here is a comprehensive primer on the background, some of the key players, how they view the current standoff, and what they hope to gain from it.

1.
Civil war? Really?

Speaker of the House John Boehner (R) of Ohio and House Republican leaders emerge from a closed-door strategy session at the Capitol Wednesday.

J. Scott Applewhite/AP

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The GOP measure to fund government past Sept. 30, while defunding "Obamacare," is expected to come to a House vote Friday, then is virtually certain to go nowhere after that.

It’s not the first time that Congress has skidded close to a "fiscal cliff." But what complicates this high-stakes showdown is the civil war in GOP ranks that, for the moment, is running against the official House GOP leaders.

Divisions in GOP ranks are so stark that it’s no longer clear who, if anyone, on the House GOP side has the clout to work out a deal and make it stick.

In the past, party leaders would take such a dispute behind closed doors, bang out a deal (in consultation with key caucus members, or not) and at the 11th hour – any sooner would smell of capitulation – present the caucus with a fait accompli, often with a lineup of powerful outside interests prepared to help enforce it.

On Wednesday morning, this template cracked. The House GOP leadership team came into a closed caucus meeting with options to avoid a government shutdown. (Congress hasn’t passed any of the 12 spending bills for the new fiscal year, which begins Oct. 1.)

But this time, a critical mass of tea party and libertarian-leaning Republicans, with their own powerful conservative backers, weren’t buying it. As a result, House GOP leaders, declaring unity, took up the insurgent plan. Immediately, civil war broke out again, this time between House insurgents and the Senate tea party stars seen as goading them to this course of action. (More on this later.)